The present invention relates to organic electronic devices that are protected from environmental elements such as moisture and oxygen.
Organic electronic devices including circuits, for example, organic light emitting diodes, organic electrochromic displays, organic photovoltaic devices and organic thin film transistors, are known in the art and are becoming increasingly important from an economic standpoint.
As a specific example, organic light emitting devices (xe2x80x9cOLEDsxe2x80x9d), including both polymer and small-molecule OLEDs, are potential candidates for a great variety of virtual- and direct-view type displays, such as lap-top computers, televisions, digital watches, telephones, pagers, cellular telephones, calculators and the like. Unlike inorganic semiconductor light emitting devices, organic light emitting devices are generally simple and are relatively easy and inexpensive to fabricate. Also, OLEDs readily lend themselves to applications requiring a wide variety of colors and to applications that concern large-area devices.
In general, two-dimensional OLED arrays for imaging applications are known in the art and typically include an OLED region, which contains a plurality of pixels arranged in rows and columns. FIG. 1A is a simplified schematic representation (cross-sectional view) of an OLED structure of the prior art. The OLED structure shown includes an OLED region 15 which includes a single pixel comprising an electrode region such as anode region 12, a light emitting region 14 over the anode region 12, and another electrode region such as cathode region 16 over the a light emitting region 14. The OLED region 15 is disposed on a substrate 10.
Traditionally, light from the light-emitting layer 14 passed downward through the substrate 10. In such a xe2x80x9cbottom-emittingxe2x80x9d configuration, the substrate 10 and anode 12 are formed of transparent materials. The cathode 16 and cover 20 (i.e., barrier), on the other hand, need not be transparent in this configuration.
Other OLED architectures are also known in the art, including xe2x80x9ctop-emittingxe2x80x9d OLEDs and transparent OLEDs (or xe2x80x9cTOLEDsxe2x80x9d). For top-emitting OLEDS, light from the light emitting layer 14 is transmitted upward through cover 20. Hence, the substrate 10 can be formed of opaque material, while the cover 20 is transparent. In top-emitting configurations based on a design like that illustrated in FIG. 1A, a transparent material is used for the cathode 16, while the anode 12 need not be transparent.
For TOLEDS, in which light is emitted out of both the top and bottom of the device, the substrate 10, anode 12, cathode 16 and cover 20 are all transparent.
Structures are also known in which the positions of the anode 12 and cathode 16 in FIG. 1A are reversed as illustrated in FIG. 1B. Such devices are sometimes referred to as xe2x80x9cinverted OLEDSxe2x80x9d.
In forming an OLED, a layer of reactive metal is typically utilized as the cathode to ensure efficient electron injection and low operating voltages. However, reactive metals and their interface with the organic material are susceptible to oxygen and moisture, which can severely limit the lifetime of the devices. Moisture and oxygen are also known to produce other deleterious effects. For example, moisture and oxygen are known in the art to increase xe2x80x9cdark spotsxe2x80x9d and pixel shrinkage in connection with OLEDS.
With the aid of a sealing region 25, the cover 20 and the substrate 10 cooperate to restrict transmission of oxygen and water vapor from an outer environment to the active pixel 15. Typically, the cover 20 is attached to the substrate 10 via sealing region 25 under a clean, dry, inert atmosphere.
Sealing region 25 is commonly an epoxy resin adhesive. Epoxy resins, however, are typically not flexible, rendering these materials undesirable for use in connection with flexible OLEDs (or xe2x80x9cFOLEDSxe2x80x9d). In addition, because they are typically inflexible, because they are not pressure sensitive, and because they are typically applied in liquid form, epoxy resins are not readily adaptable for use in web-based manufacturing techniques. Moreover, epoxy resins frequently contain ingredients that are deleterious to OLEDS. Analogous difficulties are encountered in organic electronic devices other than OLEDS.
The above and other challenges of the prior art are addressed by the present invention.
According to a first aspect of the invention, an organic electronic device structure is provided, which comprises: (a) a substrate layer; (b) an organic electronic region disposed over the substrate layer; (c) a pressure sensitive adhesive layer disposed over the organic electronic device; and (d) a barrier layer disposed over the adhesive layer. In many preferred embodiments, the organic electronic device region is an OLED region.
The adhesive layer can be disposed over all or a portion of the organic electronic region. For example, the adhesive layer can be, for example, in the form a continuous layer that is disposed over the entire organic electronic region or in the form of a ring that is disposed over only a portion of the organic electronic region.
The adhesive layer may be, for example, a low-temperature-curable adhesive layer. In preferred embodiments, the adhesive layer is a radiation-curable adhesive layer, more preferably an ultraviolet-radiation-curable adhesive layer. The adhesive layer also preferably displays low out-gassing of harmful species, as defined hereinbelow.
In many embodiments, the organic electronic device structure will include a getter material, which can be provided within the adhesive region, if desired, or elsewhere.
Preferred substrate layers, and barrier layers, for use in the organic electronic device structures of this aspect of the present invention include metal layers, semiconductor layers, glass layers, ceramic layers, polymer layers and composite material layers. Where a composite material layer is selected, it preferably comprises (a) a polymer substrate sub-layer and (b) at least two alternating pairs of high-density sub-layers and planarizing sub-layers. The planarizing sub-layers may be the same or different from each other, as can the high-density sub-layers.
In some instances, it is preferred to include a protective layer between the organic electronic region and the adhesive layer of the organic electronic device structure. The protective layer comprises, for example, a material selected from a silicon oxide, a silicon nitride, a silicon oxynitride, a metal oxide, an organic compound and an organometallic compound. As another example, the protective layer comprises one or more high-density sub-layers and one or more planarizing sub-layers.
In other embodiments, one or more spacer structures are provided between the substrate layer and the adhesive layer to prevent the adhesive layer from physically damaging the OLED region.
According to a second aspect of the present invention, an organic electronic device structure is provided, which comprises: (a) a substrate layer; (b) an organic electronic region disposed over the substrate layer; (c) a barrier layer disposed over the organic electronic region; (d) a pressure sensitive adhesive layer disposed over the substrate layer and over the barrier layer; and (e) an additional layer disposed over the adhesive layer. In many preferred embodiments, the organic electronic device region is an OLED region.
The adhesive layer in accordance with this aspect of the invention can be disposed over all or a portion of the barrier layer. The adhesive layer can be, for example, in the form a continuous layer that is disposed over the entire barrier layer or in the form of a ring that is disposed over only a portion of the barrier layer.
As above, the adhesive layer may be, for example, a low-temperature-curable adhesive layer. In some preferred embodiments, the adhesive layer is a radiation-curable adhesive layer, more preferably an ultraviolet-radiation-curable adhesive layer. The adhesive layer also preferably displays low out-gassing of harmful species, as defined hereinbelow.
Also as above, preferred substrate layers for use in the organic electronic device structures of this aspect of the present invention include metal layers, semiconductor layers, glass layers, ceramic layers, polymer layers and composite material layers. Where a composite material layer is selected, it preferably comprises (a) a polymer substrate sub-layer and (b) at least two alternating pairs of high-density sub-layers and planarizing sub-layers. Preferred barrier layers are composite material layers that comprise at least two alternating pairs of high-density sub-layers and planarizing sub-layers. The above planarizing sub-layers may be the same or different from each other, as can the high-density sub-layers.
The additional layer in accordance with this aspect of the invention can have, for example additional barrier properties, scratch resistant properties, antireflective properties and/or circular polarizing properties. The latter properties are particularly preferred where the organic electronic device structure is a transparent OLED device structure or a top-emitting OLED device structure.
According to yet another aspect of the invention, a method for providing an organic electronic device structure of provided. The method comprises: (1) providing a first region comprising (a) a substrate layer and (b) an organic electronic region provided over the substrate layer; (2) providing a second region comprising at least one additional layer; and (3) adhering the first region to the second region using a pressure sensitive adhesive layer. In this aspect of the invention, the organic electronic region is provided over the substrate layer prior to contacting the first region with the adhesive layer. In many preferred embodiments, the organic electronic device structure is an OLED structure.
The method can be, for example, a roll-to-roll processing method, allowing for continuous device production.
In many preferred embodiments, the first region is adhered to the second region by a method comprising: (a) providing an adhesive-primed region comprising (i) the adhesive layer and (ii) one of the first and second regions; and (b) contacting the adhesive-primed region with the other of the first and second regions. In these embodiments, the adhesive layer can be transferred from a release liner to either the first or the second regions to form the adhesive primed region.
In some embodiments, a barrier layer is provided with the first region, in which case the organic electronic region is positioned between the substrate layer and the barrier layer. The second region in these embodiments can comprise, for example, a layer having additional barrier properties, scratch resistant properties, antireflective properties, and/or circular polarizing properties. In other embodiments, a barrier layer is provided within the second region.
During production, gas bubbles can become trapped (a) within the adhesive layer or (b) between the adhesive layer and either or both of the first and second regions. In either case, it is preferred to remove such bubbles, for example, by applying one or more of (a) heat, (b) pressure and (c) vacuum.
Analogous to the above, the adhesive layer is preferably cured without the application of high temperatures. In some preferred embodiments, the adhesive layer is subjected to a radiation-curing step, more preferably, to an ultraviolet-radiation-curing step.
An advantage of the present invention is that organic electronic structures are provided, which are effective in protecting sensitive device components from oxygen, moisture and other harmful species in the surrounding atmosphere.
Another advantage of the present invention is that organic electronic structures are provided, which afford protection from these harmful species, while at the same time being flexible and conformable to other surfaces, if desired.
Another advantage of the present invention is that organic electronic structures are provided, which contain adhesive systems that are not deleterious to the protected device components.
Still another advantage of the present invention is that organic electronic structures are provided, which are amenable to continuous processing techniques, such as web-based (e.g., roll-to-roll) manufacturing methods.
These and other aspects, embodiments and advantages of the present invention will become readily apparent to those of ordinary skill in the art upon review of the disclosure to follow.